Numerous attempts have been made to formulate laundry detergent compositions that have both good cleaning properties and also textile softening properties so as to avoid the necessity of using a separate rinse-added textile softener product in addition to the usual laundry detergent. As cleaning by definition involves the removal of material from the textile surface and as textile softening normally involves deposition of material onto the same surface, these attempts have necessarily required a compromise in formulation to be reached between cleaning and softening performance.
The most common commercially available organic textile softening compounds are cationic materials that are reactive towards the anionic surfactants used in conventional laundry detergents. If both types of material are formulated in a single product, they tend to interact on addition to a wash liquor and, although in some instances the resulting complex has useful textile softening properties, its formation normally depresses the cleaning performance of the formulation and is therefore generally considered undesirable.
In order to overcome this problem, compositions have been proposed which have sought to minimise the mutual reactivity of the anionic and cationic materials by the addition of compatibilising compounds as described for example in U.S. Pat. Nos. 3,886,075 and 3,954,632.
An alternative approach has been to incorporate one of the reactant materials in a form that inhibits its contact with the other in the wash liquor and examples of this type of formulation are taught in U.S. Pat. Nos. 3,936,537 and 3,644,203. The performance of these compositions is however sensitive to the washing conditions that are employed. In an attempt to avoid the reactivity problem altogether, nonionic surfactants have been proposed in place of the conventional anionic surfactants and compositions of this type are described in e.g. British Pat. No. 1,079,388, German Auslegeschrift No. 1,220,956 and U.S. Pat. No. 3,607,763. However it has been found that levels of nonionic surfactant sufficient to provide good cleaning impair the softening of the cationic softener. Another proposal to provide acceptable cleaning and textile softening by avoiding the surfactant-softener interaction has been made in British Pat. No. 1,514,276 which teaches the use of certain long chain tertiary amines that are nonionic in character at the wash liquor pH existing when a conventional laundry detergent is used. The commonly-assigned European Patent Application No. 11340 published May 28, 1980 and British Application No. 7923527 filed July 5, 1979 respectively also disclose cleaning and softening compositions comprising a combination of a long chain tertiary amine and a smectite-type clay in an anionic surfactant based detergent. The use of smectite-type clays as softening agents in detergent compositions is taught in British Pat. No. 1,400,898. This type of softening agent does not affect the cleaning performance of the detergent composition but, if used on its own, requires a high level of incorporation for effective softening performance possibly because the deposition of the clay on fabrics is not very efficient in the presence of anionic surfactants.
In summary therefore the prior art attempts to provide detergent compositions having textile softening capability have been of two general types. The first type has employed cationic fabric softening additives in anionic-surfactant based compositions and has sought to achieve the best compromise between these antagonistic components. The second type has replaced one or other of these components by a substitute which is not antagonistic but which is not capable of providing the same level of performance.
The current practice in providing a fabric softeners benefits to fabrics in domestic laundering operations is to add a cationic fabric softener either as a liquid to the final rinse of the washing process or as a separate additive to a hot air tumbler dryer. Although this avoids direct antogonism between the cationic softener and the anionic surfactants conventionally used in laundry detergents, some decrease in fabric whiteness occurs because of the yellowing effect of the deposited fabric softener.
It has now been found that detergent compositions can be formulated which have cleaning performance equivalent to that of commercially available heavy duty laundry detergents together with textile softening performance that approaches that of rinse added fabric softeners without the yellowing effect normally associated with the use of such softeners.